The present invention relates to a method of operating an anti-lock automotive vehicle brake system for driving stability control and/or traction slip control, including a pneumatic brake power booster operable irrespective of the driver's wish and a master brake cylinder connected downstream of the brake power booster, the pressure chambers of the master brake cylinder being connected to wheel brakes associated with the individual vehicle wheels by way of an ABS hydraulic unit having a return pump.
German patent No. 42 08 496 discloses a brake system, wherein the brake power booster interacts with a solenoid valve to achieve automatically controlled braking operations along with a great deceleration of the vehicle. The solenoid valve permits an enhanced use of the braking pressure upon quick application of the brake pedal. A brake pedal position sensor, a brake light switch and a force sensor permitting detection of the driver's wish for deceleration are provided to achieve the above-mentioned braking pressure control concept. Further, the known brake system includes an anti-lock control system (ABS) which ensures a stable deceleration behavior of the vehicle during braking operations.
However, the patent referred to hereinabove does not provide any specific indications as to how the described brake system could be used for driving stability control.
German patent application No. 42 32 311 discloses a hydraulic vehicle brake system with an anti-lock control device having an auxiliary-pressure source for the improvement of the vehicle directional stability, in particular when cornering, by automatic braking. The auxiliary-pressure source is used to prefill the vehicle wheel brakes and to precharge the return pump. The auxiliary-pressure source, which is provided by parallel connection of an auxiliary pump, a throttle and an auxiliary-pressure limiting valve, is connected to an inlet port of one hydraulic cylinder each. The hydraulic cylinder is connected to the connection between the outlet of an actuating unit, comprised of a brake power booster and a master cylinder inserted downstream of the master cylinder, and the ABS hydraulic unit or the wheel brake. A second inlet of the cylinder is connected to the master brake cylinder, and a separating piston which can be acted upon by auxiliary pressure is guided in the cylinder. The separating piston accommodates a valve which is open in its inactive position and permits a connection between the master brake cylinder and the wheel brake. When the auxiliary pump is started, the separating piston is displaced, with the result that the valve closes the above-mentioned connection and the pressure fluid volume conducted by the separating piston causes prefilling of the wheel brakes and precharging of the return pump.
A disadvantage of this brake system is, however, the comparatively extensive technical effort and structure required to achieve the known method.